I. Field of the Invention
This invention pertains to an apparatus and method for forming battery terminal connectors through a side wall of a battery.
II. Description of the Prior Art
In U.S. Pat. No. 3,849,203 a Method For Producing Battery Terminals is disclosed. In the patent abstract, the terminal is described as including "a specialily designed lead bushing adapted to be inserted through a side wall opening from the inside of the battery case. A portion of the bushing projects beyond the outside surface of the case and is surrounded by a lead locking ring. Disposed within the bushing is a hard wear-resistant, internally threaded metallic nut used in connecting the terminal to an external cable. By means of a spinning operation, the outer edge of the bushing is forced down and over the locking ring forming an integral assembly between the terminal and side wall of the battery."
Problems can occur in attaining and maintaining a good seal between a terminal connector and a battery wall when they are assembled together mechanically. The battery is full of electrolyte which will leak through small holes or openings which might be present between metal and plastic interfaces unless special adhesives are applied, or unless steps are taken to compress the parts of the terminal together against the battery wall. See U.S. Pat. Nos. 3,798,071 and 3,457,118. Connecting and re-connecting external conductors to the battery terminal can result in mechanical loosening of the pressure bond between the metal terminal and plastic or non-metal battery wall.
A different method for producing side wall battery terminals is disclosed in U.S. Pat. No. 3,874,933. As in the first method, a battery container is provided with an opening adapted for receiving the side wall terminal. The mold assembly is then formed about the opening and molten metal is then delivered under pressure through a sprue hole into the die cavity defined by the mold assembly, is circulated through the cavity and flows out of the die cavity through a second sprue. The second sprue terminates in a cavity reservoir located in a portion of the mold assembly which reservoir receives the bulk of the lead which does not remain in the die cavity. This method requires that a quantity of lead which is 3.0 to about 6.0 unit volumes of metal per unit volume of the die cavity or terminal size be used to make the terminal.
It is desirable in making batteries to minimize the amount of lead used in the battery manufacture. Hence, it would be desirable to eliminate the requirement for a reservoir or to use 3.0 to 6.0 times the amount of lead needed for the terminal, as described in U.S. Pat. No. 3,874,933.
Another problem that occurs when casting battery terminals into a mold cavity about a wall opening in the battery is that the opening into the cavity may become clogged with lead as it solidifies. When this happens, a small jagged projection is formed on the inside surface of the battery terminal where the battery terminal is to be connected to the battery straps which must be broken away from the apparatus when the part is removed. This often results in the extra step of eliminating the jagged projection on the battery terminal so that the mating and connection between the terminal and the straps can be accomplished.